1. Field
The present disclosure relates generally to composite structures and, in particular, to inspecting composite structures. Still more particularly, the present disclosure relates to a method and apparatus for inspecting composite structures to identify porosity in the composite structures.
2. Background
Aircraft are being designed and manufactured with greater and greater percentages of composite materials. Composite materials are used in aircraft to decrease the weight of the aircraft. This decreased weight improves performance features such as payload capacity and fuel efficiency. Further, composite materials provide longer service life for various components in an aircraft.
Composite materials may be tough, light-weight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in a polymer resin matrix. The fibers may be unidirectional or may take the form of a woven cloth or fabric. The fibers and resins may be arranged and cured to form a composite structure.
Using composite materials to create aerospace composite structures may allow for portions of an aircraft to be manufactured in larger pieces or sections. For example, a fuselage in an aircraft may be created in cylindrical sections to form the fuselage of the aircraft. Other examples include, without limitation, wing sections joined to form a wing or stabilizer sections joined to form a stabilizer.
In manufacturing composite structures, layers of composite material may be laid up on a tool. The layers of composite material may be comprised of fibers in sheets. These sheets may take the form of, for example, without limitation, fabrics, tape, tows, or other suitable configurations for the sheets. In some cases, resin may be infused or pre-impregnated into the sheets. These types of sheets are commonly referred to as prepreg.
The different layers of prepreg may be laid up in different orientations and different numbers of layers may be used depending on the desired thickness of the composite structure being manufactured. These layers may be laid up by hand or by using automated lamination equipment such as a tape laminating machine or a fiber placement system.
After the different layers have been laid up on the tool, the layers may be consolidated and cured upon exposure to temperature and pressure, thus forming the final composite structure. Thereafter, the composite structure may be inspected to ensure that inconsistencies are not present. The inspection may be performed using ultrasound testing, infrared testing, visual inspections, and other suitable types of testing.
This testing may be performed to identify various potential inconsistencies in the composite structure. For example, inconsistencies may include delamination, voids, undesired levels of porosity, and other types of inconsistencies.
With respect to porosity levels, increasing porosity in a composite structure may result in a less than desired load that the composite structure is able to withstand and perform as desired. Thus, a composite structure may be inspected using ultrasound testing to ensure that the porosity level is within a desired level for the composite structure.
Currently, when ultrasound testing is used to determine the porosity of the composite structure, the entire surface of the composite structure may be inspected. For example, an ultrasound system may perform ultrasound testing to gather data from all of the surfaces of each composite structure. This data may then be analyzed by an operator to identify the porosity of the composite structure. This inspection of the entire surface of the composite structure may take more time and manpower than desired.
Further, the analysis of the data of cross-sections with non-parallel surfaces may add to the time and manpower needed to inspect these composite structures. As a result, ultrasound testing of composite structures may take more time and may cost more than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as possibly other issues.